Database Reference
In-Depth Information
Chapter 4
Malaria and Sickle Cell Anemia
4.1 Malaria
4.1.1 Basic Malaria Model
Malaria is one of the most severe human diseases, causing more than 300-500
million cases today
1
, leading to an estimated 2.7 million deaths worldwide with
80-90% of those occurring in the section of Africa below the Sahara Desert. Chil-
dren ages one to four are most vulnerable to malaria due to their immature im-
mune systems. Malaria is caused by a parasite transmitted to humans or animals by
the
Anopheles
mosquito. The human parasite,
Plasmodium falciparum
, digests the
hemoglobin found in red blood cells (RBCs) and breaks down the adhesive proper-
ties of the cells. Therefore the RBCs may become stuck to the walls of capillaries.
When this occurs in the cerebral section of the brain, cerebral malaria develops,
and blood clots in the brain occlude the vessels. Symptoms of malaria increase in
severity each time an RBC bursts and releases more parasites. These symptoms can
include high fever, chills, and uncontrollable shaking/shivering, also called rigors.
Severe headache, vomiting, muscle pain, and extreme tiredness may accompany
these symptoms as well. To combat the disease, many countries use an insecticide
called DDT to control mosquito populations. Different medications have also been
developed to treat and prevent malaria. These include chloroquine, doxycycline, and
mefloquine.
Several variables are implicated in the epidemiology of this disease. In this chap-
ter we develop a simplified model to investigate the dynamics of the spread of
malaria in a closed ideal region without human immigration. We further assume
that humans are the most important hosts and disregard other possible hosts aside
from the mosquitoes, which pick up the malaria parasites when they feed on the
blood of an infected human. Upon receipt of malaria parasites (
Plasmodium sp.
),
1
Martens,P.,R.S.Kovats,S.Nijhof,P.deVries,M.T.J.Livermore,D.L.Bradley,J.Cox,andA.J.
Mitchel. 1999. Climate change and future populations at risk of malaria. Global Environmental
Change. 9:S89-S107.
